About Cameos
Cameo is a method of carving an object such as an engraved gem, item of jewelery or vessel made in this manner. It nearly always features a raised (positive) relief image; contrast with intaglio, which has a negative image. Originally, and still in discussing historical work, cameo only referred to works where the relief image was of a contrasting color to the background; this was achieved by carefully carving a piece of material with a flat plane where two contrasting colors met, removing all the first color except for the image to leave a contrasting background.
Today the term may be used very loosely for objects with no color contrast, and other, metaphorical, terms have developed, such as cameo appearance. This derives from another generalized meaning that has developed, the cameo as an image of a head in an oval frame in any medium, such as a photograph.
Ancient and Renaissance cameos were made from semi-precious gemstones, especially the various types of onyx and agate, and any other stones with a flat plane where two contrasting colors meet; these are "hardstone" cameos. In cheaper modern work, shell and glass are more common. Glass cameo vessels, such as the famous Portland Vase, were also developed by the Romans.
Modern cameos can be produced by setting a carved relief, such as a portrait, onto a background of a contrasting color. This is called an assembled cameo. Alternatively, a cameo can be carved by the traditional, but far more difficult, method directly out of a material with integral layers or banding, such as (banded) agate or layered glass, where different layers have different colors.
Sometimes dyes are used to enhance these colors.
Cameos are often worn as jewelry, but in ancient times were mainly used for signet rings, although the largest examples were probably too large for this, and were just admired as objets d'art. Stone cameos of great artistry were made in Greece dating back as far as the 3rd century BC. The Farnese Tazza (a cup) is the oldest major Hellenistic piece surviving. They were very popular in Ancient Rome, especially in the family circle of Augustus. The most famous stone "state cameos" from this period are the Gemma Augustea, the Gemma Claudia made for the Emperor Claudius, and the largest flat engraved gem known from antiquity, the Great Cameo of France.
The technique has since enjoyed periodic revivals, notably in the early Renaissance, and again in the 18th and 19th centuries. The Neoclassical revival began in France with Napoleon's support of the glyptic arts, and even his coronation crown was decorated with cameos.
In Britain, this revival first occurred during King George III's reign, and his granddaughter, Queen Victoria, was a major proponent of the cameo trend, to the extent that they would become mass produced by the second half of the 19th century.
Information about Cameos from Wikipedia